I know that my local chapter (Santa Clara Valley) of the CA Native Plant Society is very supportive of this endeavor. They are an excellent resource for helping in finding professionals in design, install and maintaining schoolyard learning places. I am sure many areas have such groups...of course the catch would be use of plants native to the area, which only makes sense. Most groups have 100's of people whose knowledge one could tap when thinking about creating an outdoor learning area.
My personal experience from my chapter: a landscape architect designed our native garden, she then got someone to draw up a blueprint, she also came out for several work days to be on site supervisor during the install; thru the group I found several nurseries who either donated or gave discounts on native plants; and I've had several workdays over the years where 'experts' on native plants came out and supervised small groups of kids in planting more areas or doing on-going maintenance. All services provided were donated.
Drawing from these people's personal (as a hobbyist I have been gardening with native plants at home and school for about 15 years, many who helped have been doing it for twice that time) and professional experience (many folks in native plant groups do these things for a living) is a resource that reading a thousand books would not provide.
Design is also specific to an area, another reason why tapping locals is better than using books. I know there are several books about CA native plant gardens, but like most books, they are specific to CA and often even more specific to a certain area of CA.
BC, Canada has a similar program. I believe it was called "Greening the School Grounds". The intent was to turn some parts of the schoolyard back to nature so it could be used to study nature and inspire kids.
In addition, I used to offer hands-on nature programs in the classroom and schoolyard. I used these areas when they existed or we used local parks kids could walk to.